Head to the 'My events' tab of your dashboard. Next to the event for which you'd like customers to be able make a donation to your organisation while purchasing tickets for, click 'Donations'

From here you can create a new donation plan, add suggested donations and assign it to your event

Customers will always be able to choose to not give a donation and donate an amount of their own choosing

Each donation plan will be saved so you can assign it to as many events as you like without having to create it again. If you modify a donation plan for one event, all events that use that donation plan will show the modified survey

The amounts donated by your customers will be presented in your sales reports which you can view and download at any time